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| Titel |
Phosphorus limitation reduces hypoxia in the northern Gulf of Mexico: results from a physical-biogeochemical model |
| VerfasserIn |
Laurent Arnaud, Katja Fennel |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090250
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| Publikation (Nr.) |
 EGU/EGU2014-4472.pdf |
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| Zusammenfassung |
| In the northern Gulf of Mexico, excess dissolved inorganic nitrogen and phosphorus loads
from the Mississippi-Atchafalaya River system promote high primary production and
contribute to the seasonal development of hypoxic bottom waters on the Louisiana Shelf.
While phytoplankton growth is considered to be typically nitrogen-limited in marine waters,
phosphorus limitation has been observed in this region during peak river discharge in spring
and early summer. Here we present a synthesis of recent investigations that quantitatively
assessed, using a realistic physical-biogeochemical model, the effect of phosphorus limitation
on primary production and hypoxia development in the Mississippi-Atchafalaya River plume.
Our model simulations indicate that phosphorus limitation delays and displaces
westward a portion of river-stimulated primary production and depositional fluxes,
resulting in a redistribution of respiration processes toward the western Louisiana
Shelf. Despite this redistribution, phosphorus limitation did not promote a westward
expansion or relocation of hypoxia, as some had previously speculated. Rather, the
onset of hypoxia was delayed and the size of the hypoxic zone reduced. In other
words, P limitation diluted the effects of eutrophication on the Louisiana shelf.
Simulations with altered nutrient river loads show that despite phosphorus limitation,
the co-reduction of nitrogen and phosphorus remains the best strategy to reduce
hypoxia. Yet, a 50% reduction in both nutrients was not sufficient to meet the Gulf
Hypoxia action plan goal of a 5 -
103 km2 hypoxic area in our model simulations. This
result emphasizes the need for a drastic co-reduction of N and P loads from the
Mississippi-Atchafalaya River system to significantly reduce hypoxia in this region. |
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